It is proposed to extend for five years an on-going research program on the solution equilibria and kinetics of Schiff bases derived from pyridoxal and alpha amino acids or pyridoxamine and alpha keto acids. Reactions will be studied in the presence and absence of chelating metal ions, and the work will be extended to other forms of vitamin B6 (pyridoxal phosphate and pyridoxamine phosphate). Investigations underway that will be completed during the early stages of the proposed pogram and (1) threonine aldolase model reactions involving pyridoxal Schiff bases of several naturally occurring amino acids and their functional derivatives; (2) the mechanism of vitamin B6-catalyzed beta-elimination reactions as a function of amino acid structure; (3) the mechanism of decarboxylation alpha-amino and alpha-keto acids as mediated by pyridoxal (with and without metal ions), and (4) overall equilibrium studies of Schiff base formation and metal Schiff base chelate formation involving alpha amino acids and alpha keto acids and the four forms of vitamin B6 stipulated above, followed by the use of a high-speed computer to provide distributions of individual solution species as a function of pH, initial concentrations and ratios of solution components, and other solution conditions. These calculations are considered essential for the proper design of kinetic experiments, and for the deduction of detailed reaction mechanisms. The following new projects are proposed: (1) a detailed kinetic and mechanistic study of the vitamin B6-catalyzed elimination of electronegative groups from the gamma-position of amino and keto acids; 2) a study of amino acid oxidase systems; 3) a 13C-nmr investigation of how the reactivities of carbon atoms in amino and keto acids are influenced by Schiff base formation with pyridoxal, and by metal chelation of the Schiff bases; 4) kinetic and mechanistic studies of the pyridoxal and phosphate catalyzed of peptides.